The present invention relates generally to semiconductor integrated circuits. More particularly, it pertains to devices and methods to selectively transfer a high-voltage signal in a charge pump circuit.
Integrated circuits often require supply voltages of greater potential than that provided by an external voltage source (external supply). Memory circuits such as dynamic random access memories (DRAMs) and video DRAMs require higher internal voltages to pre-charge memory word lines and the like. Flash memories may require high voltages for programming operations, such as erasing. Integrated circuits that are dependent upon a limited external power supply, such as a battery, must generate additional supply voltages using conversion circuitry. Charge pumps have been used as on-chip voltage generators capable of providing a voltage more positive than the most positive external supply or more negative than the most negative external supply.
In certain circumstances, the external supply may already be at a high voltage level already. One such circumstance includes life-cycle testing of an integrated circuit during the manufacturing process. Life-cycle testing includes a high-voltage, high temperature test to eliminate integrated circuits that have an undesired probability of failure within a predetermined amount of time. In this test, the charge pump may generate from the high-voltage external supply an even higher voltage level than intended. This higher voltage level may cause damage to an integrated circuit, that otherwise may not have the undesired probability of failure, which reduces the yield of saleable integrated circuits during the manufacturing process.
Several techniques have been introduced in an attempt to alleviate the problem, including the use of diode clamps and diode stacks. However, these techniques are engaged after the integrated circuit has built up a potentially damaging level of voltage, making the effectiveness of these techniques questionable. Additionally, these techniques cannot be turned on or off as needed.
Thus, what is needed are devices and methods to selectively control the generation of high voltages in charge pump circuits.
The above mentioned problems with charge pump circuits and other problems are addressed by the present invention and will be understood by reading and studying the following specification. Devices and methods are described which accord these benefits.
An illustrative embodiment includes a charge pump circuit. The charge pump circuit includes a gating stage to generate a gating signal; the gating stage includes at least one boosting stage to boost the gating signal to a predetermined level of energy. The charge pump circuit further includes an output stage having a first, a second, and a third connection; the first connection of the output stage is receptive to a high-voltage signal; the second connection of the output stage is coupled to the gating stage to receive the gating signal; and the third connection presents the high-voltage signal. The charge pump circuit further includes a bypass stage coupled to the gating stage to selectively act upon the boosting stage so as to allow the output stage to output a desired level of the high-voltage signal.
Another illustrative embodiment includes a charge pump circuit. The charge pump circuit includes a gating stage to generate a gating signal; the gating stage includes at least one boosting stage to boost the gating signal to a predetermined level of energy; the boosting stage includes a delay stage to assist the boosting stage to boost the gating signal to the predetermined level of energy. The charge pump circuit further includes an output stage having a first, a second, and a third connection; the first connection of the output stage is receptive to a high-voltage signal; the second connection of the output stage is coupled to the gating stage to receive the gating signal; and the third connection presents the high-voltage signal. The charge pump circuit further includes a bypass stage coupled to the gating stage to selectively act upon the gating stage so as to bypass the delay stage.
Another illustrative embodiment includes a charge pump circuit. The charge pump circuit includes a phase generator to generate a first and a second phase. The charge pump circuit further includes a gating stage to generate a gating signal; the gating stage includes a first and second boosting stage to boost the gating signal to a predetermined level of energy. The charge pump circuit further includes a high-voltage generator to provide a high-voltage signal; the high-voltage signal includes a first and a second main energy-storing device. The charge pump circuit further includes an output stage coupled to the gating stage; the output stage receives and outputs the high-voltage signal; the output stage includes a first and a second output device. The charge pump circuit further includes a bypass stage coupled to the gating stage to selectively act upon the gating stage so as to allow the output stage to output a desired level of the high-voltage signal; the bypass stage includes a first and a second bypassing circuit.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.